The invention relates to a component placement machine comprising
a machine frame over which printed circuit boards can be transported and on which the printed circuit boards can be fixed, which machine frame is provided with a guide member over which a slide can be moved, PA0 a placement head for placing components on the printed circuit boards, which placement head is coupled to the slide, PA0 a linear motor for driving the slide along the guide member in a drive direction, which motor has a stationary part and a movable part, which movable part is connected to the slide.
Such a component placement machine is known from WO-A1-97/38567. The principle of such a machine is diagrammatically represented in FIGS. 5 and 6, which show, respectively, a plan view and a side view of the machine. The stationary part 7 of the linear motor 5, i.e. a magnetic chuck, is rigidly attached to the machine frame 1. During operation, the coils, which constitute the movable part 6 of the linear motor and are situated on the slide, are energized in order to drive the slide 2 along the guide member 3. As a result, a reactive force is exerted on the magnetic chuck, which force is transmitted to the machine frame. These forces are largest during starting and stopping of the slide. The machine frame starts vibrating and hence also the printed circuit board 8 which is fixed onto the machine frame. The size of the frequency of the vibration and of the amplitude of the vibration are governed to a substantial degree by the size of the reactive forces and the rigidities and masses of the various machine parts. The machine parts serve as a mass-spring system. When the vibrations come close to the natural frequency of such a mass-spring system, unacceptable vibrations having large amplitudes may develop in the machine frame. The position where a component 9 must be placed on a printed circuit board by means of the placement head 4, which is attached on the slide 2, is determined by means of a vision system (not shown). However, said vision system cannot take into account the vibrations of the printed circuit board. The placement of a component takes place immediately after the slide has stopped, i.e. within, for example, approximately 10 .mu.m. Since such vibrations generally do not damp out within this time interval, nor damp at least to an amplitude of a few .mu.m, an inaccuracy occurs during the placement of the component. Postponing the placement until the vibrations have decreased to an acceptable level is unacceptable because it leads to an unacceptable increase of the process time.